The treatment of human skin with various agents has been undertaken for many years with the goal being to keep the skin in a smooth and supple condition. Skin has the tendency to dry out when exposed to low humidity or to harsh detergent solutions for extended periods of time. From a physiological standpoint, dryness is a measure of the water content of the skin. Under normal conditions, the water content and vapor pressure of the epidermis are higher than those of the surrounding air with consequent evaporation of water from the skin surface. Skin becomes dry because of excessive loss of water from its surface which results in loss of water from the stratum corneum. Low humidity speeds up this process, exacerbating the drying of skin.
Continuous and prolonged immersion in soap or detergent solutions may contribute to dryness of the stratum corneum. The reason for this is that the surfactant medium promotes dissolution of the skin surface lipids, the horny layer lipids, and the dissolution of the hygroscopic water-soluble components in the corneum layer.
In attempts to alleviate or prevent the aforementioned conditions, many different emollient materials have been suggested for topical application to the skin. See, for example, Sagarin, Cosmetics, Science and Technology, 2nd Edition, Vol. 1, pages 34-36 (1972). The emollient materials are believed to increase the state of hydration of the corneous layer of the skin by altering the rate of diffusion of water from the lower epidermal and dermal layers, the rate of evaporation of water from the skin's surface, and the ability of the corneum layer to hold moisture.
Numerous other references disclose materials which are purported to be effective skin conditioners. However, the most effective and widely-used materials, such as glycerol, suffer from negative aesthetic qualities (e.g., greasiness or stickiness). Conversely, materials with better aesthetics tend to be ineffective skin conditioners. Therefore, the need exists for materials which can meet both efficacy and aesthetic criteria. Such materials would find immediate application, for example, in a facial moisturizer product where aesthetic properties are extremely important.
It is an object of the present invention to provide specific propoxylated glycerol derivatives which possess both excellent skin conditioning and aesthetic properties.
It is an object of the present invention to provide skin conditioning compositions, containing these propoxylated glycerol derivatives, which possess both excellent skin conditioning and aesthetic properties.
It is another object of this invention to provide skin cleansing compositions containing these propoxylated glycerol derivatives, which are effective skin cleansers and are also highly effective skin conditioners.
It is a further object of the present invention to provide methods for effective conditioning/cleansing of the skin.
These and other objects will become apparent from the description to follow.
As used herein, all parts, percentages and ratios are by weight unless otherwise indicated.